Malignant tumors are often treated by surgical resection of the tumor to remove as much of the tumor as possible. Infiltration of the tumor cells into normal tissue surrounding the tumor, however, can limit the therapeutic value of surgical resection because the infiltration can be difficult or impossible to treat surgically. Radiation therapy can be used to supplement surgical resection by targeting the residual tumor margin after resection, with the goal of reducing its size or stabilizing it. Radiation therapy can be administered through one of several methods, or a combination of methods, including external-beam radiation, stereotactic radiosurgery, and permanent or temporary interstitial brachytherapy. The term “brachytherapy,” as used herein, refers to radiation therapy delivered by a spatially confined radioactive material inserted into the body at or near a tumor or other proliferative tissue disease site. Owing to the proximity of the radiation source, brachytherapy offers the advantage of delivering a more localized dose to the target tissue region.
Brachytherapy can be performed by implanting radiation sources directly into the tissue to be treated. Brachytherapy is traditionally carried out using radioactive seeds such as 125I 103Pd seeds. These seeds, however, produce spatially inhomogeneous dose distributions. In order to achieve a minimum prescribed dosage throughout a target region of tissue, numerous radioactive seeds must be used, resulting in high doses being delivered in regions in close proximity to the seed (seeds which can cause radionecrosis in nearby healthy tissue) and relatively under-dosed spots between source positions.
One brachytherapy technique (i.e., intracavitary brachytherapy) uses a mechanical means of separating the radiation source from the surrounding tissues in order to reduce the amount of tissue exposed to the highest doses of radiation (e.g., the tissue that would have been in contact with the source). One such brachytherapy technique is balloon brachytherapy for post-lumpectomy patients. The current practice of balloon brachytherapy requires a minimum distance between the outer surface of the tissue proximate to a surgical extraction site (e.g., the lumpectomy cavity margins) and a patient's sensitive body tissues in order to avoid overexposure of such tissues.
Thus, it would be desirable to create a threshold distance between the outer surface of the tissue proximate to a surgical extraction site and a patient's skin in order to avoid overexposure of the skin during the brachytherapy procedure.